Got smelly hot water that reeks like rotten eggs? Learn the common causes, easy fixes, and prevention tips for every home. Stop the stink and get clean, safe hot water again with this clear guide.

Quick Answer: What Causes Smelly Hot Water?

That rotten egg odor in hot water usually comes from hydrogen sulfide gas. It forms when harmless but smelly sulfur bacteria react with sulfate in your water supply, or when the anode rod inside your water heater reacts with minerals. Warm water makes the odor stronger, which is why the smell shows up in hot water first. The problem is common, fixable, and often preventable with a few smart steps.

Is Smelly Hot Water Dangerous?

In most homes the sulfur odor is more of a nuisance than a health risk. At low levels hydrogen sulfide smells bad but is not known to cause illness from normal use like showering or washing. That said, strong and sudden sulfur odors can signal well water issues, heavy bacterial growth, or a failing water heater. If you smell rotten eggs and also see discolored water, experience nausea or headaches, notice the water looks oily, or your gas appliance pilot keeps going out, stop and call a pro. For emergencies in Lake County IL or Kenosha County WI, Watertight Plumbing offers 24 or 7 service at (847) 623-6810 in Lake County and (262) 484-4520 in Kenosha County.

How to Confirm the Source of the Rotten Egg Smell

Simple checks before you start repairs

  • Run only the cold water for 60 seconds at a sink. If the cold does not smell but the hot does, the water heater is the likely cause.
  • Test several fixtures. If only one faucet smells, clean that faucet aerator and the supply lines may be to blame.
  • Fill a clear glass with cold water, step away from the tap, and smell it again in another room. If the cold water smells in the glass, your source water may have sulfur issues.
  • If you are on a private well, ask neighbors if they notice odors. Seasonal changes can spike sulfur bacteria in wells.
  • Check if the smell is strongest after the water heater sits unused, like after a vacation. Stagnant water encourages odor.
  • Look at your water heater age. Units older than 8 to 12 years are more likely to develop anode rod reactions and sediment buildup.

Common Causes of Rotten Egg Odor in Hot Water

Sulfate reducing bacteria in the water heater

These naturally occurring bacteria thrive in warm, low oxygen water and feed on sulfate. They produce hydrogen sulfide gas, which smells like rotten eggs. Sediment in the bottom of the tank gives them more places to grow.

Reaction with the anode rod

Most tank water heaters have a sacrificial magnesium or aluminum anode rod that protects the tank from rust. In some water chemistry, especially where sulfate levels are higher or the water is softened, the anode reacts and increases hydrogen sulfide production. This is one of the most common triggers of smelly hot water.

Stagnant or low use water

If your home sits empty or you have infrequently used bathrooms, hot water can become stale and give odors time to form. Even a perfectly working heater can smell after a long break from use.

High sulfate well water

Homes on private wells may have naturally higher levels of sulfate. That does not mean unsafe water by itself, but it does mean the heater is more likely to produce a sulfur smell without treatment.

Cross contamination or sewer issues

Rarely, a cross connection between drain lines and supply lines can cause strong odors. A persistent sewer smell that affects both hot and cold water or that appears at multiple fixtures can point to a sewer vent or drain problem, not the heater. This calls for a professional inspection.

Water softener interactions

Softened water can increase anode activity and sometimes makes the smell worse. If the resin bed is fouled or set incorrectly, it may contribute to sulfur odors in hot water.

Fast Fixes You Can Try Today

Always use caution around hot water and electricity or gas. If you smell gas, hear hissing, or see water leaking heavily, call Watertight Plumbing for 24 or 7 emergency service. If the situation is stable, try these proven steps to reduce or remove odor from smelly hot water.

Flush your water heater to remove sediment

  1. Turn off power at the breaker for electric units. Set the gas control to pilot or off on gas units.
  2. Close the cold water supply valve to the heater.
  3. Attach a garden hose to the drain valve and run it to a floor drain or outside where hot water will not cause damage.
  4. Open a hot water faucet in the home to break vacuum, then open the drain valve. Let the tank drain fully until the water runs clear.
  5. Briefly open the cold water supply valve to stir up remaining sediment, then drain again.
  6. Close the drain valve, remove the hose, open the cold supply, and leave a hot faucet running until air is out and the flow is steady. Restore power or relight per the manufacturer.

Flushing removes sediment and bacteria pockets. Many homeowners notice a big improvement in smelly hot water after a thorough flush.

Disinfect the tank with hydrogen peroxide

  1. Turn off power or set gas to pilot. Close the cold water supply.
  2. Relieve pressure by opening a hot water faucet, then open the temperature and pressure relief valve briefly to make sure there is no pressure.
  3. Open the hot water side on the nearest faucet and remove the cold water inlet flex line at the top of the heater, or remove the anode rod if it is easier to access. Use a funnel to pour in 1 to 2 pints of 3 percent hydrogen peroxide for a 40 gallon tank. Use a bit more for larger tanks in the same ratio.
  4. Reconnect the line or anode. Open the cold water supply and fill the tank.
  5. Run several hot water faucets until you smell a mild peroxide scent, then close them and let the tank sit for 2 hours.
  6. Flush the tank thoroughly with fresh water, then restore power or relight the gas.

Hydrogen peroxide breaks down into water and oxygen, leaves no strong aftertaste, and is a plumber favorite for odor control. It is often safer for components than bleach solutions.

Heat shock to reduce bacteria

  1. Set the thermostat to 140 F for a short period, usually 2 to 4 hours. Do not exceed safe times and warn household members about scald risk.
  2. Open each hot water fixture for a few minutes during this period to bring the hotter water to the lines and fixtures.
  3. After the heat shock, return the thermostat to a safer setting, typically 120 F, especially if you have children or older adults in the home.

Raising temperature can reduce bacteria levels that cause smelly hot water. Pair this step with flushing for the best results.

Clean faucet aerators and showerheads

  1. Unscrew aerators and showerheads and soak them in white vinegar for 30 to 60 minutes.
  2. Scrub off debris, rinse, and reinstall.
  3. Run hot water for a few minutes to refresh the lines.

Mineral and biofilm buildup can trap odors near the outlet and make smells worse at certain fixtures.

Lasting Solutions to Eliminate the Smell

Replace the anode rod with aluminum zinc or a powered anode

If your anode rod is magnesium, it may be driving the odor. Replacing it with an aluminum zinc alloy rod often reduces the reaction that makes hydrogen sulfide. A powered anode, which uses electricity instead of a sacrificial metal, is even more effective and does not create the same odor issues. This upgrade is a top fix for recurring smelly hot water and protects the tank from corrosion. Watertight Plumbing can inspect your current anode, recommend the right replacement, and install it safely.

Install the right water treatment for your water chemistry

For well water or municipal supplies with high sulfate or iron, treatment can prevent the smell from ever reaching the heater. Options include:

  • Activated carbon filtration to reduce odor and taste issues.
  • Oxidation and filtration systems that convert dissolved sulfur into filterable solids.
  • Chlorination with retention and carbon filtration for serious sulfur bacteria problems.
  • Air injection systems for sulfur and iron reduction.
  • UV disinfection for bacterial control in well water.

A water softener helps with hardness but can make anode reactions worse in some cases. If you have a softener and persistent odor, have the system settings and resin condition checked. Watertight Plumbing can coordinate water testing and match treatment to your exact problem.

Service or replace an aging water heater

Units with heavy corrosion, frequent pilot outages, or repeated odor returns after treatment may be at the end of their useful life. Upgrading to a new gas, electric, or tankless system can solve odor issues and improve efficiency. Watertight Plumbing installs and maintains gas, electric, and tankless water heaters and can help you choose the right capacity, venting, and efficiency for your home or business.

Prevention Tips to Keep Odors Away

  • Flush your water heater every 6 to 12 months to remove sediment.
  • Maintain a storage temperature of 130 to 140 F if safe for your household to discourage bacterial growth. Use mixing valves or set back to 120 F when needed for scald safety.
  • After vacations, run hot water at each fixture for a few minutes to clear stagnant water.
  • Inspect and replace the anode rod every 3 to 5 years, or sooner if you have smelly hot water or very hard or softened water.
  • Sanitize the tank annually with hydrogen peroxide if you have a history of sulfur odors.
  • Test well water yearly for bacteria, sulfate, iron, and hardness, and adjust treatment accordingly.
  • Clean faucet aerators and showerheads twice a year to remove biofilm and mineral buildup.
  • Have your water softener serviced and set to match your hardness level to avoid over softening that can heighten odor reactions.

When to Call a Professional Plumber

DIY steps cover most cases, but some warning signs mean you should bring in a pro. Call Watertight Plumbing if:

  • The rotten egg smell is in both hot and cold water.
  • The smell is very strong, you see discolored or cloudy water, or you notice slimy film in sinks and tubs.
  • Your water heater is leaking, making loud popping noises, or the pilot light will not stay lit.
  • You smell natural gas or see scorch marks near a gas heater. Leave the area and call for emergency service.
  • The odor returns within days after flushing or sanitizing.
  • You are unsure how to replace an anode rod or safely relight a gas water heater.

Watertight Plumbing, also known as Water Tight Plumbing and Sewer, is a family owned company with more than 30 years of experience. Our licensed, bonded, and insured team provides 24 or 7 emergency help, expert water heater service, sewer and drain cleaning, and complete plumbing repairs. We serve homes and businesses across Kenosha, Zion, Waukegan, Gurnee, Libertyville, and nearby communities. Call (847) 623-6810 for Lake County or (262) 484-4520 for Kenosha County.

FAQs About Smelly Hot Water

Why does only my hot water smell like rotten eggs?

The heat in your water heater speeds up reactions that create hydrogen sulfide gas. Bacteria and the anode rod have more effect in hot water than in cold. If cold water smells fine but hot water stinks, focus on flushing, sanitizing, and the anode rod.

Is it safe to shower if my hot water smells like sulfur?

Most of the time it is safe, but it will be unpleasant. If the odor is strong, if you feel unwell, or if you have well water with known sulfur problems, fix the issue first or call a pro. Children, older adults, and people with breathing issues may be more sensitive to strong odors.

Can I remove the anode rod to stop the smell?

Removing the anode rod might reduce odor for a short time, but it leaves your tank unprotected from corrosion and can shorten its life. A better solution is to replace it with an aluminum zinc anode or a powered anode. Watertight Plumbing can perform the swap and check for any other contributors to the smell.

Do tankless water heaters get the rotten egg smell?

Tankless units are less likely to produce sulfur odors because there is no large storage tank. However, if your source water has sulfur or your plumbing has biofilm, you may still notice some smell at fixtures. Treating the source water and descaling the unit on schedule will help.

Will a water softener help or make it worse?

A softener helps with scale and protects fixtures, but in some homes it increases the reaction at the anode rod that produces hydrogen sulfide. If you have a softener and smelly hot water, consider an anode change and verify the softener settings are correct for your water hardness.

How much does it cost to fix smelly hot water?

Costs vary by cause. A basic flush and sanitize is usually the least expensive. Anode rod replacement is a moderate cost and is one of the most effective long term fixes. Treatment systems or water heater replacement cost more but can solve persistent or whole house problems. Watertight Plumbing provides clear estimates after a quick diagnostic and can advise on the most cost effective path.

Get Fast, Reliable Help in Lake County and Kenosha County

Smelly hot water does not have to be your new normal. Whether the cause is a reactive anode rod, sulfur bacteria, or a well water issue, the right steps can remove the odor and keep it from coming back. Watertight Plumbing brings more than 30 years of experience to water heater repairs, installations, and maintenance for gas, electric, and tankless systems. We also handle emergency plumbing, sewer rodding and camera inspections, sump pumps and battery backups, and full service plumbing for new construction and remodeling. If you live in Kenosha, Zion, Waukegan, Gurnee, Libertyville, or a nearby community, call us today at (847) 623-6810 in Lake County or (262) 484-4520 in Kenosha County. Our licensed, bonded, and insured team is ready 24 or 7 to stop the stink and restore clean, fresh hot water to your home or business.